Status change detection apparatus



Sept. 20, 1966 D. E. STARK 3,274,577

STATUS CHANGE DETECTION APPARATUS Filed oct. 18, 196s l 641411 0S l am, N

United States Patent C) 3,274,577 STATUS CHANGE DETECTION APPARATUS Donald E. Stark, Eastwood, Pa., assigner to Westinghouse Air Brake Company, Swissvale, Pa., a corporation of Pennsylvania Filed st. 18, 1963, Ser. No. 317,309 2 Claims. (Cl. 340-213) My invention relates to status change detection apparatus. More particularly, my invention pertains to an improved circuit arrangement for detecting a change in the condition of an indicated function through the action of this function to change the position of a single-pole, singlethrow contact, this contact also being used to give character to an indication of the condition of the function.

-In many prior art remote control systems, an open transfer contact is used to detect changes in the condition of each remote function for which indications are transmitted to the control oiiice. In other words, a transfer contact is used to provide a status change detection which initiates t-he transmission of indications in the remote control system as a result of the open circuit time occurring when the transfer contact shifts its position. IFor example, such operation is shown in the remote control systems disclosed in 'Letters Patent of the United States No. 2,698,425, issued Dec. 28, 1954, to A. B. Miller, and in Letters Patent of the United States No. 2,411,375, issued Nov. 19, 1946, to A. P. Iackel. The use of this prior art type of starting circuit, that is, the open transfer contact, is not limited, however, to remote control systems of the time code type. -In these prior fart remote control systems, use is also made of special continuity transfer contacts to provide a brief audible signal indication, such as a single stroke bell signal, to call the attention of the system operator to a change in a particular indication which does not warrant the use of a continuous audible alarm requiring specific acknowledgement to terminate.

In many of the earlier remote control installations, since all of the apparatus was new, transfer contacts of the type needed for status change detection of audible signal control could readily be made available in accordance with the number and type needed. As remote control systems are appplied to existing industrial processes and/ or transportation services, the problem has arisen lthat transfer contacts can not be made available on the existing apparatus, the conditions of which must be indicated from the remote locations to the control oce. This problem arises because the vsame manufacturer may not provide all of the apparatus, particularly where a portion is previously in service as an existing system. The apparatus is thus made to different standards of use and design. It 4has been found 'that quite frequently only singlepole, single-throw contacts (hereafter usually referred to as SPST contacts) are available for indicating function changes and for characterizing the indications which are transmitted by the remote control system. IOf course, repeater relays of the SPST contacts can be used to pro- Vide transfer contacts. This arrangement, however, Islows the action of the indication system since any repeater relay interposes some pickup time into the elapsed action time. More important, the use of repeater relays for every indication contact adds additional expense to the installation of the remote control arrangement. 'It is of considerable advantage, therefore, if the available SPST contacts maybe used directly to both indicate a change in the status of the function and vthe character of the condition of the function. Another advantage is the use of a single indication storage contact at the oice to provide both registry of that indication and control for an audible signal denoting the reception of an indication change.

3,274,577 Patented Sept. 20, 1966 ICC Accordingly, an object of my invention is improved status change detection apparatus.

Another object of my invention is an improved circuit arrangement for detecting a status change in an indication function.

It is also an object of my invention to provide a status change circuit arrangement which will detect a change in a function as recorded lby the change in position of a single-pole single-throw contact.

A still further object of my invention is an indication circuit arrangement using one single-pole single-throw contact to provide character to the registra-tion and/or display of the condition of an indicated function and also to control an audible alarm device to sound a brief signal of each function condition change.

Still another object of my invention is an improved code starting circuit arrangement for remote control systems which will detect a function status change as recorded only Iby the changing position of a single-pole single-throw contact.

A further object of my invention is a circuit arrangement for remote control systems which is controlled to start -the transmission of an indication code in response to the movement of a single-pole single-throw Contact, one such contact being provided for each indication function, each Contact also characterizing the information transmitted for the assigned function `by the indication code.

Other objects, features, and advantages of my invention will become apparent from the following specification when taken in connection with the accompanying drawmgs.

I shall now describe three circuit arrangements embodying forms of my invention and shall then point out the novelty thereof in the appended claims. In this following description, reference will be made from time to time to the accompanying drawings in which:

lFIG. l is a diagrammatic illustration of a code starting circuit arrangement for a remote control system which detects changes in the status or position of SPST contacts representing t-he state of the functions to be indicated and which circuit arrangement embodies one form of my invention.

fFIG. 2 is a similar illustration of a modification of the circuit arrangement of FIG. 1 to incorporate solid state devices in the status change detection portion of the code starting arrangement.

FIG. 3 is another form of the circuit arrangement of IFIG. 1 adapted to control indication registry and alarm devices at the code receiving location of the remote control system.

In each of the drawings, similar reference characters designate similar parts of the apparatus. Also in each of the circuit arrangements shown, a local source of direct current energy is provided but is not specifically shown since the use of such energy sources is conventional in the art and any well known type may be used. Throughout the drawings, however, connections to the positive and negative terminals of the direct current energy source are designated by the reference characters B and N, respectively.

In practicing tmy invention, the status change detection is accomplished in the illustrated forms by utilizing the charge and discharge current of a storage capacitor. The current flow is directed by half-wave rectiers or diodes through a device, shown as a relay, which will briefly register each change in the function. In the code starting arrangement, a SPST contact is used t-o represent a two Astate function, control `of the contact by the function being by any well known means. The closed and open positions of the SPST contact thus designate the two opposite states of the represented function whose status change is to be detected. The status change registry device used in the form illustrated is an auxiliary starting relay which may be of the biased type although this is not necessary. The closing of the function-representing contact completes the circuit for charging the storage capacitor through a properly poled diode with the auxiliary start relay winding included in this charging circuit. When this auxiliary relay picks up, it ac-tuates the usual starting relay of the remote contr-ol system to initiate the indication coding action. In the specific form illustrated, the pickup of the auxiliary relay opens a stick circuit of the normal starting relay so that this latter relay releases to accomplish the code starting action or, under system busy conditions/co store a code starting action. When the function restores to its original position so that its function-representing contact opens, the removal of the charging potential allows the storage capacitor to discharge. This discharge circuit includes a resistor and a second diode and the winding of the auxiliary start relay. The diode is so poled that the current direction is controlled to again energize the starting relay, the charge and discharged circuits being separa-ted by the half-wave rectifier diodes. Again, the pickup of the auxiliary starting relay tactuates the normal starting relay to initiate the coding action.

In using the circuit arrangement for indication display and alarm purposes, the charge and discharge of the storage caipacitor is effected by the movement of the SPST indication registry contact between its two positions. This activates a relay which controls the alarm circuit. Each time the relay operates, an alarm is actuated. However, since the relay operation, that is, pickup, is of relatively brief duration, the alarm sign-al is of limited length as is the usual practice of such systems. Solids state circuitry may also be incorporated into the function status detection arrangement. Under these conditions, the charge and discharge actions of the storage capacitor are use-d to control one shot multivibrator devices. In turn, these multivibrator devices then control the auxiliary .starting relay with the remainder of the action being as previously described.

I shall now describe in detail the three different arrangements Which embody forms of my invention.

Referring to FIG. 1, shown therein is a basic form of the circuit arrangement of my invention used in a code starting arrangement for a remote control system, this starting arrangement being in use at eac-h of the Iremote stations of such a control system. In the upper left of this figure, two SPST contacts are shown, designated as contacts 1I and 21. .Each of these contacts represents a separate function having two states or conditions. Each change in the state'of these functions is to be indicated by the remote control lsystem to a central ofce location. Obviously, each contact represents the existing state or condition of the associated function as the contact is in its closed or open position. Such control of these indication contacts is Well known in the rem-Ote control art and no detailed arrangement for this control is necessary in the present showing.

Each contact, when closed, completes a direct connection from terminal B of the local source to the line coding unit of the remote control system. This connection is used to characterize the existing condition of the function during the transmission of an indication code from that station location. Half-Wave rectiiers or diodes D7 and D8 are inserted in the-se circuits in order to prevent any flow of current in the reverse direction which would incorrectly inuence the code starting arrangement to be discussed hereinafter. For purposes of this description, the remote control system is assumed to be that illustrated in the aforementioned Miller Patent No. 2,698,425. Particular reference is made to the various parts of FIG. 2 of this Miller patent which illustrate the circuit arrangement at a remote station of such a remote control system. Tio provide a specific reference to the showing in this patent, the code step characterizing leads illustrated in FIG. l are designated by the reference characters 139 and 140 which correspond to equivalent leads originating in FIG. 2d of the Miller patent. Upon reference to the patent, it will be noted that no half-Wave reictiers or diodes are included in the equivalent leads in the basi-c reference system. Such devices are unnecessary since the function characterizing circuits in this prior art 'are separate from the code starting or function change detection arrangement and no sneak circuit paths-are possible.

The code starting relay ST shown in the lower part of FIG. l is equivalent to the similar relay ST shown in FIG. 2c of the Miller patent. However, it is to be noted that, in the circuit arrangement of my invention, no reactor coil is connected in mult-iple with the winding of relay ST to assist in the rapid release of the relay. Nor is it necessary that the relay be of the biased type since the sensitivity to reverse current flow and the rapid action characteristics of such biased relays are not he-re required. Relay ST is normally energized by a stick circuit which may be traced, `as shown in somewhat conventional fashion, from terminal B at the back contact of continuity transfer contact e of station relay S, over lead 182, the back contact of continuity transfer contact c of bridging relay LB, lead 183, front contact a and the Winding of relay ST, lead 216, Iand back contact a of an auxiliary lstarting relay STA to terminal N of the source. As explained in the Miller patent, the stick circuit may at times extend over other paths including front contact c of relay LB or lfront contact e of relay S and leads 236 and 159 together with contacts of the station receiving relay SR and the station line relay R. The stick circuit arrangement shown in FIG. 1 between terminal B and the Winding of relay ST is copied exactly from that shown in the Miller reference patent. However, in the patent, lead 216 extends to terminal N over various open transfer contacts of function repeater relays, there being one such open transfer contact for each function to be indicated lfrom that station. As previously mentioned, these transfer contacts are separate and distinct from the function characterizing contacts in the Miller system. Here, the action of both types of contacts are combined in a single SPST contact such as contacts 1I and 2l in the upper left, there being one such contact for each reportable function.

lIn the stick circuit arrangement shown in the present system, it is obvious that the opening of bac-k contact a of relay STA will deenergize starting relay ST. Upon re- Ilease, the closing of bac-k contact b of relay ST completes the connection from terminal B to lead 147. As shown in detail in the patent, this circuit further extends over various checking contacts to Ithe station master relay M, which must be energized in order to initiate coding action from this location. In the present system, relay ST is provided with the usual energizing circuit which includes front contact f of master relay M, lead 232, front contact c of chain'repeat relay CR, front contact e of counting chain relay 8, lead 206, the winding of relay ST, lead 216, and back contact a of relay STA. As explained in the Miller reference, this circuit is completed during indication coding action at this station to reenergize relay ST, which then picks up to complete its own stick circuit which at various times may be completed to terminal B over any one of the various paths illustrated. For a full understanding of the operation -of these stick and energizing circuits of relay ST and the action of relay ST in initiating a code transmission, reference is made to the Miller patent. It is believed that sufficient description is included herein, together wth 4the circuits illustrated, to allow a full understanding of the arrangement of the present invention.

lIt is apparent from the preceding circuit description that auxiliary starting relay STA must respond to, that is, must register, each function change in order to start indication coding action at this location. To illustrate this, it is assumed that indication contact I1I closes to repeat a change in the status of the represented function. With contact 1I closed, a charging circuit is completed 'for storage capacitor O1. This circuit may be traced from terminal B over contact 1I in its closed position, through capacitor O1, diode ior half-wave rectiter D1, the winding lof relay STA from right to left, and diode D5 to terminal N. Since the winding of relay STA is included in this charging circuit, it is obvious that 'the initial flow of charging current will energize relay STA so that it picks up. As long as contact 1I remains closed, potential continues to be applied to hold capacitor C1 charged, the upper plate of this capacitor having the positive polarity. It is obvious, of course, that the level of current flow in the charging circuit rapidly decreases until the capacitor is fully charged when no current will ow in the previously traced circuit. As the current flow decrea-ses, it reaches a point at which insufcient energy is supplied to the winding of relay STA to hold the relay picked up. This relay then releases and remains released as long as capacitor C1 remains fully charged. It is thus apparent that, during the charging action, relay STA picks up and then releases, thereby opening, for at least a brief period, its back contact a. This interrupts the stick circuit for relay ST, which releases to initiate the transmission of an indication code from this station. Relay ST, of course, will be' reenergized during the transmission of this code by the previously traced energizing circuit in a manner conventional to such systems.

It is now assumed that contact 1I opens, in response to the return of the represented function to its initial state or condition. No potential is now available to hold capacitor C1 charged and .this capacitor now discharges through a circuit traced from the upper terminal of capacitor O1 through resistor R1 to terminal N, continuing from terminal N through diode D6, the winding f re'lay STA from right to left, and diode D3 to the lower plate of capacitor C1. The initial current flow through this discharge circuit energizes relay STA, which picks up to open its back contact a to again release relay ST. Resistor R1 provides a time constant to this discharge circuit to hold relay STA picked up for a sufticient period to assure the release of starting relay ST, even though this latter relay is of an ordinary neutral type. It is to be noted that relay STA is indicated a-s a bi-ased relay and that, in the illustrated circuit arr-angements, the current -flow is always in the same direction through the relay Winding. However, it is not absolutely necessary that this relay be of the biased type since the circuit parameters may be so arranged that relay STA will assuredly pick up during the period of current flow.

Similar status change detection circuits are provided for contact 2l. Without tracing in detail, it is apparent that circuits are provided for the charge and discharge of storage capacitor C2, to detect position changes of contact 2L These circuits, as distinct from those previously traced, include diodes D2 and D4 and resistor R'Z. The circuit path through the winding of relay STA and the paths through diodes D5 and D6 are common portions of the status change detection circuit arrangement for each of the two contacts illustrated. T-he circuits for detecting the change in position of all such function-representing contacts at this station are connected in multiple to control relay STA. However, each such indication contact controls a separate and distinct function characterization circuit such as those illustrated connected to leads 139 and i140. In the operation of these multiple circuit arrangements for detecting the status change of a plurality of such indication contacts, it is of little importance how long relay STA remains held up as various `contacts may change in consecutive time order. The limit-ing condition is that relay STA must cause the release of start relay ST at such times as there is a function change to be reported to the control location, even though successive indication codes may be required to complete the entire report.

Referring -now to FIG. 2, I shall describe the modified arrangement which allows the use of solid state circuitry in detecting the status changes as required. In this circuit arrangement, transistorized one shot multivibrators are used to provide suicient current `for the control of relay STA. It is to be noted, as conventionally shown, that the flow of energizing current through relay STA is always in the same direction without specific arrangements to control the current rlow ias in the circuits of IFIG. 1, that is, diode-s DS and D6 previously discussed. The use of these one shot multivibrators will Ipermit the use of smaller capacity values for storage capacitors C1 and C2 as well as shorter time constants lfor the charge and discharge circuits. As will be described, voltage pulses of the proper polarity are all that is required t-o actuate the one shot -multiv-ibrators.

In the illustrated arrangement, each one shot multivibrator lis shown by a conventional bloc-k designated OSI or OS2. Any well known form of circuits for such one shot multivibrators may be used. For example, a -speciiic multivibrator circuit suitable for use here `is shown -in FIG. 194 (page 200) of Department of the Army Technical Manual TMll-690 entitled lBasic Theory .and Application of Transistors, dated March 1959. It is to be understood, of course, that the type of circuit referred to will be modified in order to allow the use of positive or negative input pulses, as may be available. It is apparent `from a study of the drawi-ng-s that various changes have been made from the basic circuit arrangement shown in FIG. l. The lower plate of each of the storage capacitors C1 and C2 is tied through a resistor to terminal N of the local source. The input to each one shot multivibrator from the corresponding diode network is through an isolating and coupling capac-itor used to generate the voltage pulse. These capacitors are designated as C3 and C4, respectively, for multivibrators OSI and OS2.

Considering rst the circuit network for detecting a status change in contact 1I, it is `apparent that the lower plate of capacitor C1, connected through resistor R3 to terminal N, is normally, that is, with contact 1I open, held at the negative potential of terminal N. Said in another way, the junction between capacitor C1 and resistor R3, designated by the reference character 10, is held at the potential of terminal N as long as contact 1I remains open. In actuality, both plates of capacitor C1 under these conditions are held at this potential since the upper plate of this capacitor is connected through resistor R1, as previously described, to the same terminal of the local source. Assuming now that contact 1I closes, repeating a status change of the represented function, capacitor C1 is charged by the circuit extending from terminal B through contact 1I closed, capacitor C1, and resistor R3 to terminal N. At the instant of initial current ow in this charging circuit, junction point 10 assumes the full positive potential of terminal B since the capacitor has no charge at this instant and the full voltage of the source occurs across resistor R3. This positive potential of point 10 is fed through diode D1 to capacitor C3, generating a positive pulse which is applied to multivibrator CS1. As previously indicated, multivibrator OSI is designed to be actuated by such positive pulses and responds to this input by shifting to its unstable state, thus producing an output current which flows through the winding of relay STA which, thus energized, picks up. The opening of back contact a of relay STA actuates the release of start relay ST by interrupting its stick circuit as previously described. This release of relay ST initiates the transmission of an indication code from that station location. As capacitor C1 becomes charged, ow of current through the charging circuit ceases and junction 10 again assumes the potential of terminal N. Under these conditions, the full potential between terminals B and N appears across :capacitor C1 which is thus fully charged. However, thischange in the potential of junction point from that yof terminal B to that of terminal N is gradual and no negative pulse occurs in the circuit for the other multivibrator. Additionally, as will be described shortly, multivibrator OS2 is designed so that the input must be of a potential more negative than that of terminal N in (order for the multivibrator to be actuated. At the end of its preset period, multivibrator OSI restores to its vstable state and relay STA releases.

When contact 1I opens as the function which it repre- 'sents resumes its original state or condition, the connection to terminal B from the upper plate of capacitor C1 is interrupted. This removes the potential holding capacitor C1 charged and a discharge action now occurs. The circuit for discharging capacitor C1 may be traced from the upper plate of this capacitor through resistor R1 and resistor R3 to the lower plate of the capacitor. The 'full potential of the charge on capacitor C1 thus appears across the resistor combination R1, R3. Since the junction between these two resistors is held at the potential of terminal N by the direct connection thereto, junction point 10 becomes more negative than terminal N during this discharge action due to the voltage drop across resistor R3. The more negative potential of this junction point 10 feeds through diode D3 to coupling capacitor C4. This latter capacitor generates a negative pulse as an input to multivibrator OS2. As previously indicated, multivibrator OS2 is designed for actuation by negative inputs and this present pulse is of sufficient negative potential below that of terminal N to trigger the device to its unstable condition. This shift in the state of device OS2 provides an output through the winding of relay STA which is of suiicient energy Ilevel to cause this relay to pick up. Again, the pickup of this relay opens its back contact a, deenergizing relay ST which releases to initiate a coding action. When the charge on capacitor C1 has dissipated, junction point 10 returns to the negative potential of terminal N. At the end of its presetperiod, multivibrator unit OS2 restores to its stable state and relay STA releases. It may be noted that a similar circuit arrangement is provided for detecting a status change of contact ZI. Capacitor C2 is connected to terminal N through resistor R4 and the discharge circuit thus includes resistors R2 and R4. The potentials existing at junction point under the various conditions are applied through diodes D2 and D4 to coupling capacitors C3 and C4, respectively, in the same manner as described previously for capacitor Cll and point 1li.

The circuit arrangement shown in FIG. 3 is intended for use at a control office for registering indications received from the station locations and for providing an audible alarm for such indications as desired. These two features are provided for each indication using only a single indication registry contact such as contact 1K shown in the upper left of FIG. 3. It will be obvious from an inspection of FIG. 3 that the basic circuitry shown in FIG. l has been only slightly modified to allow for the visual registry of the indication and the control of the audible alarm device. When contact 1K closes, as a result of the reception of an indication code indicating the equivalent position of a remote function which this contact represents, the circuit for energizing `indication lamp lEK is completed from terminal B through contact 1K in its closed position and the filaments of the lamp lEK to terminal N. The illumination of lamp lEK designates that the corresponding function at the remote location is in a predetermined condition or state. In addition, the closing of contact iK completes a charging circuit for storage capacitor C1A which extends from terminal B over contact 1K closed through capacitor C1A, diode DIA, the winding of an alarm indication relay AK, and diode DSA to terminal N. This ow of current energizes relay AK at a sufiicient energy Ilevel to cause it to pick up, closing its front contact a to energize the audible alarm device shown'by conventional symbol. As in the 'operation described for FIG. l, as capacitor C1A becomes fully charged, current flow in the charging circuit ceases and relay AK is deenergized and releases, opening its front contact a. Thus, the audible alarm device is energized and provides an audible signal only for the brief period that relay AK is sufficiently energized to pick up. When Contact 1K opens, the connection to terminal B for capacitor C1A is interrupted and this capacitor is no longer held charged and immediately discharges. The discharge circuit may be traced from the upper plate of capacitor C1A through resistor R1A, terminal N, diode D6A, the winding of relay AK, and diode DSA to the lower plate of capacitor C1A. Sufiicient current flows as the capacitor starts its discharge to energize relay AK which picks up, again energizing the audible alarm device. The time constant of the discharge circuit is made sufficiently long by the inclusion of resistor RIA in the circuit to allow relay AK to pick up and actuate the alarm device at least for a brief period. This provides an audible signal to the system operatol of the change in the indication function .represented by contact 1K. It is to be noted that other indication registry contacts similar to contact 1K and representing the state of other functions at the remote location have equivalent status change detection arrangements connected in multiple with that described and shown for contact 1K. Each of these multiple arrangements controls relay AK in a similar manner which may be understood by considering the multiple arrangement of the function status contacts in FIG. l.

This status change detection circuit of my invention thus provides an improved arrangement for code starting in remote control systems. Only a single contact of the `SPST type is required at the remote st-ationfor each func- ,tion to both characterize the function as transmitted to the office and for the purpose =of detecting a change therein to start an indication code transmission. This makes it possible to utilize such a function representing contact already Iavailable in existing equipment when a remote control system is added for the purpose of remotely operating the existing system from a central location. No extra relay is thus required for repeating the position of the indication contact representing the state of the function at this remote location.

Although I have herein shown and described but three circuit arrangements embodying forms of the status change detection arrangement of my invention, it is to Abe understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope -of my invention. Furthermore, although these forms of my invention have each been described in connection with a remote control system, such use is for specific illustration -only and it is not my intention to limit .my invention to such use.

Having thus described my invention, what I claim is: 4 i1. Indication code starting apparatus for the remote stations of a coded remote control system, comprising at each station in combination,

(a) a condition repeating SPST contact for each twocondition indication function, operable between a closed and an open posit-ion to repeat the first and second conditions respectively of the corresponding function,

(b) a capacitor associated with each repeating contact,

v(c) an .auxiliary starting relay,

`(d) a source of direct current energy,

1(e) a first and a second one shot multivibrator device,

(f) a first circuit for each capacitor including said source, the corresponding repeating contact, the capacitor, an-d a first resistor for -charging that capacitor when said corresponding repeating contact closes,

(g) a second circuit for each capacitor including that Capaitr, the lcorresponding first resistor, and a second resistor connected in series for discharging that capacitor when the corresponding repeating contact opens,

(h) a coupling network connected between said rst multivibrator device and each capacitor for applying an actuating pulse of preselected polarity to said lirst device when a repeating contact closes,

(i) another coupling network connected between said second multivibrator device .and each capacitor for applying an actuating pulse of opposite polarity to said second device when a repeating contact opens,

(j) an energizing network for said auxiliary relay jointly controlled by said multivibrator devices for briefly energizing said relay when `a multivibrator device is actuated,

(k) a starting circuit means controlled by said auxiliary relay for initiating an indication code when said relay is energized.

2. Function change registering apparatus for a plurality of two state functions, comprising in combination,

(a) a single SPST contact associated with each of said plurality of functions and operable to a closed and an open position to repeat the rst iand second state, respectively, of the associated function,

(b) a capacitor associated with each SPST contact,

(c) an auxiliary relay,

(d) a source of direct current energy,

y(e) a first and a second one shot multivibrator device,

(f) a first circuit for each capacitor including said source, the associated contact, the capacitor, and a rst resistor for charging that ycapacitor when said associated contact closes,

(g) a second circuit for each capacitor including that capacitor, said rst and a second resistor connected in series for discharging that capacitor when said associated contact opens,

(h) a rst and a second diode poled in opposite directions associated with each capacitor,

(i) a coupling network including in parallel all said rst diodes and connected ybetween said first multivibrator device and each capacitor for applying an actuating pulse to said first device when an SPST contact closes,

(j) another coupling network including in parallel all said second diodes and connected between said second multivibrator 'device and each capacitor for applying an actuating pulse to said second device when an SPST contact opens,

l(k) an energizing network for said auxiliary relay jointly controlled by said multivibrator devices for briey energizing said relay when a multivibrator device is actuated,

(l) a registry circuit means controlled lby said auxiliary relay for registering a change in said functions each time said auxiliary relay is energized, and

(m) an indication characterizing circuit for each function including said associated SPST contact for indicating the state of that function.

References Cited by the Examiner UNITED STATES PATENTS 2,112,228 3/1938 Crago. 2,168,805 8/ 1939 Pelikan. 2,314,267 3/ 1943 Brixner 340-213 X NEIL C. READ, Primary Examiner.

R. M. ANGUS, D. J. YUSKO, Assistant Examiners. 

1. INDICATION CODE STARTING APPARATUS FOR THE REMOTE STATIONS OF A CODED REMOTE CONTROL SYSTEM, COMPRISING AT EACH STATION IN COMBINATION, (A) A CONDITION REPEATING SPST CONTACT FOR EACH TWOCONDITION INDICATION FUNCTION, OPERABLE BETWEEN A CLOSED AND AN OPEN POSITION TO REPEAT THE FIRST AND SECOND CONDITIONS REPECTIVELY OF THE CORRESPONGING FUNCTION, (B) A CAPACITOR ASSOCIATED WITH EACH REPEATING CONTACT, (C) AN AUXILIARY STARTING RELAY, (D) A SOURCE OF DIRECT CURRENT ENERGY, (E) A FIRST AND SECOND ONE SHOT MULTIVIBRATOR DEVICE, (F) A FIRST CIRCUIT FOR EACH CAPACITOR INCLUDING SAID SOURCE, THE CORRESPONDING REPEATING CONTACT, THE CAPACITOR, AND A FIRST RESISTOR FOR CHARGING THAT CAPACITOR WHEN SAID CORRESPONDING REPEATING CONTACT CLOSES, (G) A SECOND CIRCUIT FOR EACH CAPACITOR INCLUDING THAT CAPACITOR, THE CORRESPONDING FIRST RESISTOR, AND A SECOND RESISTOR CONNECTED IN SERIES FOR DISCHARGING THAT CAPACITOR WHEN THE CORRESPONDING REPEATING CONTACT OPENS, 